In computer systems, a copy, or backup, of the contents of memory associated with a computer is periodically made and stored in a so-called backup memory. This is done so that if the computer memory fails, for whatever reason, then the contents of that memory may be restored using the copy stored in the backup memory and using stored copies of computer files which changed since the backup was made. The latter copies are commonly referred to as incremental changes.
It can be appreciated that it takes an appreciable period of time to run (i.e., make) a backup copy of the contents of a very large computer memory, and during that time the associated computer system is typically not used for another purpose, since such use would interfere with the making of the backup copy. As such, a backup session is usually scheduled for a particular period of time sufficient to complete the backup during which the associated computer system is unavailable to users.